The present invention relates to direct smelting plant for producing molten metal in pure or alloy form from a metalliferous feed material such as ores, partly reduced ores and metal-containing waste streams.
A known direct smelting process, which relies principally on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International Application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application comprises:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) a metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting metalliferous feed material to metal in the metal layer.
The term xe2x80x9csmeltingxe2x80x9d is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal.
The HIsmelt process also comprises post-combusting reaction gases, such as CO and H2 released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver the solids material into the metal layer in the bottom of the vessel. To promote the post combustion of reaction gases in the upper part of the vessel, a blast of hot air, which may be oxygen enriched, is injected into the upper region of the vessel through the downwardly extending hot air injection lance. Offgases resulting from the post-combustion of reaction gases in the vessel are taken away from the upper part of the vessel through an offgas duct.
The HIsmelt process enables large quantities of molten metal to be produced by direct smelting in a single compact vessel. However, in order to achieve this it is necessary to transport hot gases to and from the vessel, to transport the metalliferous feed material to the vessel and to transport the molten metal product and slag away from the vessel all within a relatively confined area. These functions must continue throughout a smelting operation which can be extended over a long period. It is also necessary to provide access and handling facilities to enable access to the vessel and lifting of equipment between smelting operations. The present invention enables a very effective arrangement of plant by which facilities for various functions are separated into distinct zones disposed about the vessel so as to minimise the potential for interference between the various functions and to maximise safety of the smelting operations.
According to the invention, there is provided direct smelting plant for producing molten metal from a metalliferous feed material including:
a fixed smelting vessel to hold a molten bath having a metal layer and a slag layer on the metal layer and a gas space above the slag;
a solids feed means to supply metalliferous feed material and carbonaceous material into the vessel;
gas injection means extending downwardly into the vessel to inject oxidising gas into the gas space and/or the slag layer in the vessel;
gas delivery duct means extending from a gas supply location away from the vessel to a delivery location above the vessel for delivery of oxidising gas into the gas injection means;
offgas duct means for flow of offgas from an upper part of the vessel away from the vessel;
a metal tapping means for flow of molten metal from the bath during a smelting operation out of a lower part of the vessel;
a metal tapping launder to receive molten metal from the metal tapping means and to transport that molten metal away from the vessel;
slag tapping means in a side wall of the vessel for tapping slag from the bath during a smelting operation; and
slag tapping launder means to receive slag from the slag tapping means and to transport that slag away from the vessel;
wherein the oxidising gas delivery duct means and the offgas duct means extend in a first of three discrete zones spaced circumferentially about the vessel and extending outwardly from the vessel;
the metal tapping means and metal tapping launder are disposed in a second of said three zones; and
the slag tapping means and slag tapping launder means are located in the third of said zones.
Preferably, the second and third zones are disposed to mutually opposite sides of the smelting vessel and the first zone is disposed between the second and third zones circumferentially of the vessel.
Preferably too, the plant further comprises slag draining means for draining slag from the lower part of the vessel at the end of a smelting operation, the means being lower than the slag tapping means, and slag drain launder means to receive slag from the slag draining means and to transport it away from the vessel.
Preferably further, the slag draining means and the slag drain launder are located in a fourth discrete zone extending outwardly of the vessel between the second and third zones.
Preferably further, the fourth zone is disposed generally opposite to the first zone relative to the vessel.
The metal tapping means may comprise a metal flow forehearth projecting outwardly from the lower part of the vessel.
The plant may further include a metal holding means disposed away from the vessel and the metal tapping launder may extend to the holding means to deliver molten metal into the holding means.
Preferably the plant further includes gas heating means at the gas supply location to supply hot gas to the gas delivery duct means for injection into the vessel.
The gas delivery duct means may comprise a single gas duct extending from the gas supply location to the delivery location.
The solids feed means may comprise one or more solids injection lances.
More particularly, there may be a plurality of solids injection lances spaced circumferentially of the vessel. Each of the lances may extend downwardly and inwardly into the vessel through a side wall of the vessel.
The slag tapping means may comprise a pair of slag tapping notches in the side wall of the vessel.
The vessel may be disposed about a central upright axis and said zones may radiate outwardly of the central axis outside the vessel.